Dr. Paylor has identified inbred strains of mice that are very high (AKR) and very low (C57BL/6J) on Prepulse Inhibition (PPI). PPI is a measure of sensorimotor gating which is abnormal in several neuropsychiatric disorders, including schizophrenia. Poor PPI in C57BL/6J mice may provide an animal model of the deficit on prepulse inhibition seen in schizophrenia. Breeding of the AKR x C57BL/6J cross produced F2 mice, for Quantitative Trait Loci analysis of genes linked to schizophrenia-like symptoms on Prepulse Inhibition. Behavioral testing of 500 F2 mice was completed this year by Dr. Paylor and Ms. Libbey. Genotyping of the extremes of the 500 F2 mice is now in progress. Our Section collaborates with molecular geneticists in NIMH and other NIH IRPs on behavioral phenotyping of transgenic and knockout mice with mutations of genes expressed in the brain. Several of these small pilot collaborations have revealed major behavioral phenotypes relevant to mental illnesses, including PPI deficits in mice with mutations in the serotonin transporter, and in a developmental gene, dishevelled-1.